Organic electroluminescent displays are light-emitting displays that are superior to displays that may require a separate light source, such as LCDs, in terms of motion picture characteristics, viewing angle and color reproduction. For these reasons, they are attracting much attention. They exploit the phenomenon of electroluminescence, in which differential energy is discharged as light when the electronic state of a material (typically an organic electroluminescent component) is changed from a ground state to an excited state by an electric field and the electronic state is returned from an unstable excited state to a stable ground state.
In general, an organic display device may comprise a plurality of singularly addressable electroluminescent components EL, each comprising a pixel of the image. FIG. 1 is a typical drive stage of an electroluminescent component EL that comprises a pixel of an electroluminescent display. Referring to FIG. 1, a driving transistor Ml is connected to the electroluminescent component EL to supply a current for emitting light. The current flowing throughout the driving transistor M1 is controlled by a data voltage applied through a switching transistor M2. The capacitor Cst connected between the gate of the transistor M1 and a voltage reference VSUS is used to precharge the gate of the transistor M1, thereby maintaining the applied voltage for a predetermined period of time. The gate of the transistor M2 is connected to a respective control line CTL1 and the current terminal of the transistor M2 is connected to a respective data line VDATA. The transistors M3 and M4 are controlled by respective control signals CTL2 and CTL3 for respectively discharging the control node of M1 and connecting/disconnecting the transistor M1 to the electroluminescent component EL.
When the control signal CTL1 turns on the transistor M2, a data voltage VDATA, that represents a desired intensity of light to be emitted, is applied to the gate of the driving transistor M1 via the data line. A current determined by the data voltage VDATA flows throughout the electroluminescent element EL, which emits light with an intensity corresponding to the data voltage VDATA. The data voltage VDATA may assume a value contained in a predetermined range of values VGMA_L, VGMA_H, that corresponds to the range of intensity of the emitted light.
FIG. 2 is a typical high level block diagram of a control device CONTROL that generates the voltages VGMA_L, VGMA_H, between which the data voltages VDATA may move. The block SOURCE DRIVER IC is a generator of data voltages VDATA that receives at least the extreme voltages VGMA_H and VGMA_L and also a command that represents a quantized level of the variation range defined by the extreme voltages, and outputs the data voltages VDATA on a data line to correspond to the quantized level.
Typically, the control circuit receives digital words DIGITAL representing the nominal values of the extreme voltages VGMA_H and VGMA_L to be generated. These digital words are converted into respective analog voltages VH and VL by respective digital-to-analog converters DAC, which use as a reference voltage Vref a voltage generated by a stable voltage generator VBG, for example, a band-gap voltage generator. The analog voltages VH and VL are amplified by respective amplifiers in cascade, referred to ground and supplied with a supply voltage AVDD, so that the extreme voltages VGMA_H and VGMA_L are determined in function of the analog voltages VH and VL by the following equations:VGMA—H=(1+(R2/R1))*VH, andVGMA—L=(1+(R2/R1))*VL, 
R2/R1 being the fixed gain of the amplifiers.
In theory, the voltage ELVDD′ applied to the source of the driving transistor M1 should match a fixed supply voltage ELVDD supplied by a reference voltage generator. Because of losses along the relatively long electric path from the reference voltage generator to the current terminal of the driving transistor M1, as schematically represented in FIG. 3, the voltage ELVDD′ effectively supplied to the electroluminescent component EL may significantly differ from the fixed supply voltage ELVDD. Therefore, when a same data voltage is generated for different electroluminescent components EL placed in different rows in order to generate light with the same intensities, the voltages ELVDD′ applied to the driving transistors of the electroluminescent components EL may be different. Hence, a current of a different intensity flows throughout the electroluminescent components EL and thus they emit light with different intensities depending on their position in the array of the display, even if the supplied data voltages VDATA are the same. This undesirable effect may be particularly evident in high resolution AMOLED displays, that may absorb relatively great currents.